Circuit interrupter



Fel 22, 1949. .1. M. CUMMING CIRCUIT INTERRUPTER Filed Feb. l, 1945 R O T N E V m James /7 (0177/770757,

Patented Feb. 22, 194g UNITED STATES ATENT OFFICE CIRCUIT INTERRUPTER .laines M. Cumming, Turtle Creek, Ea., assigner' ,l

to ljifcstinghouse Electric Gorporation, East Pittsburgh, Pa., a corporation of Pennsylvania application February 1, 1945,1Serial No. 575,589

Winthrop M. Leeds and Benjamin P. Baker and assigned to the assignee of the instant application, there is disclosed and claimed the concept of utilizing a differential piston in a circuit interrupter spring-biased toward the open circuit position. The parent application of this divisional application is entitled Circuit interrupter and was iiled November 11, 1942, Serial No. 455,244, now U. S. Patent No. 2,465,469, issued August 27, 1946 to Leon R. Ludwig, Winthrop M. Leeds and Benjamin P. Baker, and assigned to the assignee of the instant application. vMy invention is con-r cerned with various improvements relating to this type of structure.

A more specic object is to provide an improved circuit interrupter in which piston means are utilized for facilitating the extinction of an arc, and biasing means are provided to bias the piston means toward the open circuit position. Preferably, I provide a second arc, which may be a `serially related arc, to assist the biasing means to move the piston means to the open circuit position.

Another object is to provide an improved circuit Vinterrupter of the liquid break type in which :novel piston means are empioyed to effect the extinction of one or more arcs drawn therein.

In United States Patent 2,253,9li9, which issued August 19, 1941, to Benjamin i3. Baiser, and which Was assigned to the assignee of the instant application, there is disclosed a novel circuit interrupter in which a piston member having surface irregularities and carrying the movable contact separates from a stationary contact to establish an arc. The structure is such that the arc is positioned adjacent the surface irregularities disposed on the piston member carrying the movable contact, and the piston member moves into the piston chamber which also has a plurality oi surface irregularities. The consequence of this interrupting structure is that the arc is drawin adjacent the surface irregularities on both the piston member and on the inner Wall of the piston chamber, and the uid-flovv provided by the piston action is effective to travel longitudinally of the established arc to effect the extinction thereof.

The surface irregularities provided on the piston member and on the inner Walls of the piston chamber serve to retain a plentiful supply of uid (Cl. 20d- 1150) adjacent the arc .to be acted upontto facilitate.

the lattersextinction.andalso the irregularities increase. the electrical .creepage distance .between f. .This .type of circuit interruptenv has proved .to be very effective ininterrupting relai tively low and mediumyalues of current with 1 very low arc energy. It is anobject of my invenelectrodes.

tion tomi-prove and adaptathis structure for the erruption of higher currents withoutt'ne necessity of employing heavier accelerating. springstoy provide a high enough speed for the piston member, against the back pressure fromrthe arc, to

ensure an adequate flowof oil to eiiect extinction of the are.

Further objects and advantages Willlreadily.. become apparent upon a readingcf the following specification taken in conjunction lvvith the drawing, in which:

Figure i is a circuit interrupter, partly .in section embodying my invention and shown in the closed circuit position,

Fig. 2 is an enlargedlvertcal. sectional .ViewA through `the right-hand .arc extinguishing unit of Fig. l, the parts being shownat an internieydiate point in the opening operation,

Fig. 3 .is a modied type of arc extinguishing unit whichinay be used in place ofthe unit shown in 2, the parts being shown in an intermediate terminal and suitably clamped thereto' are tivo are extinguishing generally desig natec by the reference numeral G.

The two units t are electrically interconnected in the close-:i circuit position, as shown in Figi, by a conducting cross-bar l which is reciprocally operated ina vertical 4direction by an insulating' operating rod o'ierated bya'suitable actuating mechanism, not shown.

Referring to Fig. 2, which shows more `clearly the construction of the arc extinguishing unit 6, it Will be observed that integrally formed With the contact foot 9 is a cover member iii. cover member lil is suitably secured by means, not

shown, to a conducting plate member il, having Y a portion I2 threadedly secured a-tiS to an insug, 1 thereof, the reference numeral l rdesig- The lating casing member lil. The casing member Ill supports a relatively stationary contact I5, the latter being electrically connected by a conductor I6 to the cover member Iii.

The casing member Irl Ialso supports a relatively stationary contact I'i connected by a conductor I8 to a pair of disconnect fingers I9, which may be engaged by the conducting cross-bar or bridging member l. A cover plate 2li is threadedly secured at 2l to the lower end of the casing member Iii, and assists in guiding a piston member, generally designated by the reference numeral 22. The piston member 22, shown in the middle of its stroke, is composed of insulating material and carries a conducting strap 23 having a contacting portion 2d which engages the stationary contact I'I and a contacting portion 25 which engages the stationary contact I when in the closed circuit position of the interrupter as shown by the full lines in Fig. 1.

The piston member 22 has an enlarged portion 26 which slidably moves in an enlarged portion 2l formed in the casing member lli. Immediately below the stationary contact I5 and formed in the casing member I are a plurality of surface irregularities 28. Also formed on the enlarged portion 26 of the piston member 22 above the contacting portion are a plurality of surface irregularities 29.

During the opening operation, an interrupting arc 39 is established between the contacts QS, and a pressure-generating arc 3l is established. between the contacts Il and 2Q. The pressure formed at the pressure-generating arc 3l acts through a port 32 and into a region 32 formed by removing a cylindrical portion 3A from the piston member 22. The upper portion 35 of the piston member 22 is cylindrical in shape and slidably er gages a downwardly depending cylindrical portion 36 integrally formed with the plate member II. An accelerating compression spring is disposed between the plate member Il and the piston member 22. A valve 38 is provided in the plate member I I. Also apertures 39 are provided in the plate member I I which, together with one or more apertures @-6, permit the region lll above the piston member 22 to be at substantially atmospheric pressure.

A valve l2 controls the passage of oil through a plurality of apertures t3 provided at the lower 5" end Li of the piston member 22. The valve t2 has a stem which is actuated during the closing stroke by a portion of the cross-bar or bridging member 'I'.

The operation of the arc extinguishing unit f3 will now be explained. In the closed circuit posi-- tion, the electrical circuit extending therethrough comprises terminal stud 5a, contact foot cover member IG, conductor I, stationary contact I5, contact 25, conducting strap 23, contact 2d, stationary Contact I'I, conductor I8, disconnect ngers I9 through the conducting bridging member 'I and through the left-hand arc extinguishing unit 6 in an identical manner to the other terminal stud 5a of the interrupter.

During the opening operation the bridging member 'I moves downwardly to permit the accelerating compression spring 3l to force the pis'w ton member 22 downwardly to cause a simultaneM ous separation between the contacts I5, 25 and I1, 241. This separation of the several contacts draws a pressure-generating arc 3| of constant length and an interrupting arc 3s of increasing length.

The pressure formed at the pressure-generating arc 3| acts through the port 32 and into the region 33 to assist the accelerating compression spring 3i to drive the piston member 22 downwardly. It will be observed that a cross-sectional area A of the piston member 22 is moved out of the unit 6; consequently, the piston member 22 functions as a differential piston during the opening operation.

In other words, considering Fig. 2 pressure from the pressure-generating arc 3l acts downwardly on the area A of the piston 22 moving out of the unit ii and also downwardly on the relatively small annular area fit. Also the pressure from the pressure-generating arc 3l acts upwardly on the piston 22 in the region 5I. Further, an upward force is exerted by the interrupting arc Sii on the piston 22 in the region 131. Consequently, the downward force on the small area :d8 is approximately balanced by the upward force exerted in the space 5 I, and the area A of the piston is made larger than the annular area of the piston projected in the space lil. Thus the arcing pressure, considering both arcs 3l), 3l, acts to drive the piston 22 out of the unit 6 and so assist the accelerating compression spring 3l.

During the opening operation, the interrupting arc Sii is drawn adjacent to the surface irregularities 28, 29 and is subjected to a longitudinal flow of oil, caused by the piston action of the enlarged portion 2e, moving from the region 1 below the enlarged portion 26 upwardly adjacent the interrupting arc 3Q and into the freely vented region ill which is substantially at atmospheric pressure.

It will be noted that the initial downward movement of the cross-bar 'fl permits the valve 42 to close the apertures i3 as a result of pressure within the region 33, the cross-bar '1, nevertheless, maintaining sliding electrical contact with the disconnect lingers I9.

The foregoing interruption process quickly effects the extinction of the interrupting arc 30 to interrupt the electrical circuit passing through the interrupter. Continued downward movement of the piston member 22 causes a flushing ow of fluid to pass from the region il upwardly adjacent the region between the contacts I5, 2% to iiush contaminated fluid into the freely vented region di. Also the upper end 48 of the portion 35 separates from the lower end A9 of the cylindrical portion 36 to permit a communication between the region 4I and the region 33.

The pressure within the region 33, consequently, is released and the valve 33 opens to permit fresh oil to enter the region 33 from the freely vented region 5b. Also the continued downward motion of the piston member 22 forces a ushing stream of oil from the region 5I upwardly adjacent the region between the separated contacts I?, 2:3 to flush contaminated oil which had been adjacent the pressure-generating arc 3l through the port 32 and into the now vented region 33.

When the piston member 22 strikes the cover plate 2s following circuit interruption, the conducting bridging member I separates from the disconnect ngers I 9 to introduce an isolating gap into the circuit. In the open circuit position the piston member 22 engages the cover plate 2e in abutting relation and the valve 38 is open which, together with the apertures 39, permits fresh oil to enter the regions 33, 4 I

During the closing operation, the upward movement of the bridging member l opens the valve d2 and picks up the piston member 22 to elfect a reengagement of the contacts I5, 25 and I'l, 24 to effect -a closure of the electrical circuit through the interrupter. The accelerating compression springv 31 is charged and the unit il is in a state ready for the next opening operation to occur.

From the foregoing description it will be apparent that I have provided a differential piston member 22 spring-biased to the open circuit position and have utilized a serially related pressure-generating arc 3! to assist the opening movement. The interrupting process effecting the extinction of the interrupting arc 30 is as described and claimed in United States Patent 2,253,009, which issued August 19, 1941, to Benjamin P. Baker, and which is assigned to the assignee of the instant application.

By a utilization of a serially related pressuregenerating arc, the opening operation of the unit 6 is accelerated, especially during the interruption oi high amperage currents without the introduction of additional accelerating compression springs. Consequently, the diiiculty, which was previously encountered in adapting type oi interruptor to the higher powers, has been surmounted by the construction herein disclosed of utilizing a serially related pressure-generating l arc to speed up the opening motion.

It will be observed that the pressure-generating arc'drawn between the contacts il, 3E; runs down the side 52 of the stationary contact l1 to thereby provide a controlled arc which generates power. This controlled arc makes the opening stroke mechanically automatic under all current ratings after the arc is drawn. The controlled arc merely means that `a constant pressure is available thereat at all current ratings to sup-ply the additional opening power during interruption. This method of boosting the opening force by utilizing the gas pressure formed at a pres-- sure-generating arc during interruption cuts down the load previously required to move this interruptor by spring force. This enables the breaker Vto work with less noise and minimum speed, although the initial stored spring energy is smaller than Vpreviously used.

Fig. 3 shows a modied type of arc extinguishing unit generally designated by the reference numeral 53. This unit is similar to the unit ii previously described and, consequently, similar reference numerals have, where possible, been employed. However, a second piston means, generally designated by the reference numeral 5s is provided which comprises an annular piston member .55 slidably guided by the casing niember ld and spring-biased to its upward closed circuit position by compression springs 55. Vents 51 are provided in the casing member ift which re closed by the piston member 55 during the initial downward travel thereof. Also ports 53 are provided in the cylindrical portion 35, the purpose for which will appear more clearly hereinafter.

The operation of the modied type oi are eX- tinguishing unit 53 will now be explained. The downward movement of the bridging member 1 permits the accelerating compression spring 31 to move the rst piston means 22 downwardly, establishing both an interrupting arc 33 between the contacts I5, 25 and a pressure-generating arc 3| between the contacts I1, 2d. The pressure formed at the pressure-generating arc l, as previously described, passes through the port 32 and into the region 33 to assist the accelerating compression spring 31 in driving the piston member 22 downwardly, the piston member 22 during this portion of the opening operation serving as a differential piston member. Also `the pressure within the region 33. acts upwardly to close-the valve 38 and passes through the ports `58 to act on the upper surface of the annular piston member 55, forcing said piston member downwardly to maintain superposed oil pressure .adjacent the interrupting arc 3i?. By maintaining .this superposed pressure in the region 59, .the dielectric strength of the medium surrounding the interrupting arc 30 is considerably increased, and interruption of said arc is thereby accomplished ino-re rapidly.

Considering the forces acting in Fig. .3' during the opening operation when the piston 55 covers the vents 51, it will be observed that pressure from the pressure-generating arc 3l 'tends to drive the entire tube 44 of area B out of the .unit 53. Also this pressure from the arc 3i acts upwardly on the piston 22 in the region 5I. Further the interrupting arc 30 .acts upwardlylon the piston 22 in the region 41. Preferably. ithe area B is greater than the sum of the two areas of piston 22 exposed to the regions lil, 5I so .that independently of action of the secondpiston 55, the piston 22 functions as a diierential piston. As such, the arcing pressure of the two .arcs 30, 3i assists the vaccelerating spring 31 .as was the case in Fig. 2.

By the provision of the second piston 55 .pressure from the arc 3i acts down on the :piston 55 and through the oil in the region 59v to tend to force piston 22 exposed to the region 59. downwardly. Thus the net force exerted by both .arcs

3i is downwardly tending to. assist the accelerating compression spring 31. Vents^51 remain covered by the piston 55 until interruption .of the arcs is completed.

It will be observed vthat inthe `previous embodiment 01"' my invention, as shown in :Fig..:2, the .oil passed upwardly .adjacent .the arc vZidoutof the region l1 and into the Yfreely vented region 41, The oil displaced from .the region 41 Vwas lonly sufficient in volume to nll the .region lil which enlarged as the piston member 22 in Fig..2 .moved downwardly. Consequently, in Fig. 22, .the-oil .was not maintained under superposed pressure adjacent the interrupting arc l33. However, in Fig. 3 I have provided the second piston means 5d utilizing pressure established by the pressure-generating arc 3 to maintain oil under pressure inthe region 59. Thus, 'the lin-terirupting ;arc13ll is not only aiected by oil passing upwardly from region [l1 by the piston action of the piston member 122, but also the entire V:bddy 'ofroil zwithin the .region 5S is maintained under superposed pressure by virtue of the downward travel of the Ysecond piston means following the `downward Atravel of the rst piston means 22.

Interruption quicklyensues andthe accelerating compression spring 31 continues to drive the rst piston means 22 downwardly .to provide a flushing flow of fluid adjacent the regions which were in contact with the pressure-generating arc 3l and the interrupting arc 3U. The subsidence of pressure following the interruption of the arcs 3B, 3| permits the springs 55 to retrieve the second piston means 54 to its upper closed circuit position, thereby opening the vents 51 to permit a release of pressure from the region 59 out of the unit 53 through the vents 51. The upper end 48 of the portion 35 separates from the lower end 49 of the cylindrical portion 36 to permit a communication of pressure between the regions 33, 59 and hence, through the vents 51 to the region exterior of the unit 53. The valve 38 then opens to permit residual gas to escape and fresh oil to enter the regions 33, 59 from the region 59 which is freely vented through one or more apertures #i9 to the region exterior of the unit E53.

During the closing operation, the ybridging member 7 moves upwardly to open the valve i2 and to pick up the first piston means 22 to thereby establish the circuit through the simultaneous engagement of the contacts i5, 25 and I?, 2li, thus charging the accelerating compression spring El. In this position, the unit is in readiness for the next opening operation.

From the foregoing description of the modified type of unit shown in Fig. 3, it will be observed that the eiectiveness of the unit shown in Fig. 2 is considerably improved by using the theory of are interruption under oil with super-posed pressure.

From the foregoing description it will be apparent that I have provided an improved circuit interrupter in which a differential piston is e. ployed being spring-biased to the open circuit position and in which a serially reiated pressuregenerating arc is employed to assist in the opening movement of the differentiai piston. During low current interruption, the differential piston may be moved by the spring pressure alone; during high current interruption the pressure from the serially related arc will be available to thereby facilitate opening movement of the differential piston. It will also be apparent that I have employed novel piston means to bring about superposed pressure adjacent the interrupting arc to facilitate the extinction thereof. During the opening operation there is obtained a ushing flow of uid following circuit interruption to wash contaminated fluid away from the contacts to thereby minimize the possibility of restriking of the extinguished arc.

Although I have shown and described specific structures, it is to be clearly understood that the same were merely for the purpose or illustration, and that changes and modifications may readily be made therein by those skilied in the art Without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. In a circuit interrupter, an arc extinguishing unit, a relatively stationary contact, a piston member carrying a movable Contact, opening motion of the piston member causing a separation of the movable Contact from the stationary contact to establish an interrupting arc and a forcing of ud against the same, the piston member having a surface which is drawn adjacent the arc during the opening operation, means for establishing a serially related pressure-generating arc, the pressure-generating arc facilitating the opening motion of the piston member, and second piston means operated by the pressure created at the pressure-generating arc to increase the Ipressure maintained at the interrupting arc.

2. In a circuit interrupter, an arc extinguishing unit, a relatively stationary contact, a piston member carrying a movable contact, opening motion of the piston member causing a separation of the movable contact from the stationary contact to establish an interrupting arc and a forcing of uid against the same, the piston member having a surface which is drawn adjacent the arc during the opening operation, means for establishing a serially related pressure-generating arc, the pressure-generating arc facilitating the opening motion of the piston member, second piston means operated by the pressure created at the pressure-generating arc to increase the pressure maintained at the interrupting arc, and venting means operated near the end of the opening motion of the second piston means.

3. In a circuit interrupter, an arc extinguishing unit, a relatively stationary contact, a piston member carrying a movable Contact, opening motion of the piston member causing a separation of the movable contact from the stationary contact to establish an interrupting arc and a forcing of uid against the same, the piston member having a surface which is drawn adjacent the arc during the opening operation, means for establishing a serially related pressure-generating arc, the pressure-generating arc facilitating the opening motion of the piston member, second piston means operated by the pressure created by the pressure-generating arc to increase the pressure maintained at the interrupting arc, and biasing means for retrieving the second piston means following the completion of the opening operation.

4. In a circuit interrupter, a casing member having an enlarged chamber and also a smaller chamber, a pair o relatively stationary contacts supported vby the casing member, a differential piston member having an enlarged portion and a relatively smaller portion, the differential piston being movable Within the casing member, the piston carrying a conductor which bridges the pair of relatively stationary contacts in the closed circuit position of the interrupter, the differential piston member also carrying a lpair of disconnect ingers, and an isolating member which makes electrical contact with the disconnect fingers and serves to move the differential piston member upwardly during the closing stroke.

JAMES M. CUMMING.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,147,497 Prince et al Feb. 14, 1939 2,154,515 Leeds et al Apr. 18, 1939 2,199,607 Bakken May 7, 1949 2,235,901 Ronnberg Mar. 25, 1941 2,249,977 Peniold July 22, 1941 2,372,589 Leeds et al. Mar. 27, 1945 

